If you just want to kill the fleas without putting a month-long effective chemical in their system, try Capstar pills. They will kill all fleas on the dog within 20 minutes, but it only lasts for 24 hours so its in and out of their system quickly.
I would also treat your yard with diatomaceous earth like Betty suggested. Also there are some products you can find online that you spray your yard with (connected to a water hose) that use orange peel, etc which is supposedly natural bug repellant.
We also use Bug Off Garlic in my house!